Dizzy in the third trimester

Tonight I got done working my 9 hour shift, well I was at the end of it and I got really dizzy/lightheaded, hot and nausea. I called my dr and she said its normal that my blood supply is going to the baby and less to my head. I was thinks about asking my dr to limit my working hours like maybe from 9 to 6? I don't know if she can or will do that. Is anyone else feeling this way in the third trimester?